Automatic line transfer control

ABSTRACT

An oscillatory, multi-pole, mechanically held switch has a shaft provided with a lever at one end. The lever extends into a reciprocating box-like yoke which is connected at each end to the armature of a solenoid. Energization of one or the other solenoid causes oscillation of the shaft through about 60* and throws the switch to connect load lines to either public utility lines or emergency lines. In proximity to the yoke are two normally closed micro-switches, one wired in series with each solenoid. A pin on the lever is positioned so that when either solenoid has been energized and the switch lever fully moved in proper direction by the solenoid, the pin opens the micro-switch to de-energize the solenoid. The lever may be manually actuated in emergencies when the controls for the solenoids fail.

[ 51 May29, 1973 '[73] Assignee: Electro-Motion [54] AUTOMATIC LINE TRANSFER CONTROL [751 Inventors: Erich W. Loffler; Hans Kruger,

. both of Redwood City, Calif.

Pacific, Inc., Redwood City, Calif.

22 Filed: Mar. 27, 1972 21 Appl. No.2 238,280

4/1966 Russell ..335/161 8/l9l8 Krantz ..335/180 Primary ExaminerHarold Broome Attorney-Julian Caplan, Gregg, Hendricson & Caplan {5 7] ABSTRACT An oscillatory, multi-pole, mechanically held switch has a shaft provided with a lever at one end. The lever extends into a reciprocating box-like yoke which is connected at each end to the armature of a solenoid. Energization of one or the other solenoid causes osciliation of the shaft through about 60 and throws the switch to connect load lines to either public utility lines or emergency lines. In proximity to the yoke are two normally closed micro-switches, one wired in-series with each solenoid. A pin on the lever is positioned so that when either solenoid has been energized and the switch lever fully moved in proper direction by the solenoid, the pin opens the micro-switch to dey energize the solenoid-The lever may be manually actuated in emergencies when the controls for the solenoids fail.

2 Claims, 5 Drawing Figures PATENTEU W29 3. 7 36 O54 SHEET 1 OF 2 AUTOMATIC LINE TRANSFER CONTROL This invention relates to an automatic line transfer control. The control is used with a commercially available, mechanically held line transfer control switch which is movable between two positions one wherein the utility power lines are connected to the load and the other wherein emergency power generator facilities are connected to the load in emergencies when the normal line supply is temporarily not available. The present invention provides an electromechanical means to actuate the switch between one position and the other. Equipment which is used in connection with the device, but which is not a part of the present invention, senses when any phase of the utility line voltage drops below a pre-selected point, such as 70 percent of normal. When this occurs, the sensing means starts a generator for the auxiliary source; when this source has brought the emergency line voltage up to 90 percent of needed voltage, then the present invention provides a means to throw the line transfer control switch from normal line position to emergency line position. In the event either that the emergency line voltage drops below a pre-selected point, or in the event that the normal line voltage is restored so that it buildsup to a pre-selected percentage such as 90 percent of normal voltage, then the sensor also causes the control of the present invention to throw the line transfer control switch back to normal position.

It is, accordingly, a principal purpose of the present invention toprovide solenoid control means energized depending upon the sensing of the normal line and emergency line voltages to throw the aforementioned switch between one position and another.

One of the features of the invention is that fact that the line transfer control switch, which is commercially available, need not be altered on its interior in any manner, and hence there is no impairment of the function of such switch. The switch actuating lever, moreover, is exposed for manual actuation where, for one reason or another, an operator wishes to move the switch between its two positions and thus override the solenoid control of the present invention. This feature is important in emergencies when the sensing devices have failed.

Another principal feature of the invention is the provision of switches in series with each of the two solenoids which switches are normally closed but which are held open when the switch control lever has been pulled by one of the solenoids to the full limit of its travel. Opening the normally closed switch discontinues power to the solenoid and thus the life of the solenoid is enhanced since it is not subject to current during any time but the briefinterval while the switch lever is being moved. Further, since power through the solenoid has been discontinued, it is easier to manually throw the switch lever.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is a schematic top plan view showing the device of the present invention installed on a switch which is partially shown in the drawing.

FIG. 2 is a fragmentary sectional view taken substantially along the line 2-2 of FIG. I and showing the micro-switch locations.

FIG. 3 is a fragmentary sectional view taken substantially along the line 3-3 of FIG. 1 and showing the solenoid control for the switch actuating lever.

FIG. 4 is an end elevation of a modification.

FIG. 5 is an enlarged sectional view taken substantially along the line 55 of FIG. 4.

Switch 11 is a commercially available switch, a suitable example of which is a Blue Line switch produced by Kraus & Naimer G. M. B. H. of Austria. The details of such switches are not part of the present invention and are not herein illustrated. However, such a switch has a main shaft 12 which oscillates through a travel of approximately 60 and by mechanical means such as a cam and a spring-pressed cam engaging detent is mechanically held in each of its two positions. The number of sets of switch contacts in switch 11 is subject to variation. For purpose of the present invention, it may be assumed to be a three-phase switch having three sets of contacts. Each set consists of a main, or normal, line contact which is connected to the public utility power line, an emergency contact which is connected to an emergency generator which may be diesel operated, and a load contact which is connected by buss bars to a load. Emergency power is required in many installations such as hospitals where any failure of the utility line power or the falling of the voltage thereof beyond a pre-selected percentage of normal may be very dangerous. Standby emergency equipment is available in such locations and means is provided to sense when the line voltage diminishes beyond percent of rated voltage in any phase whereupon the emergency generator prime mover is started and the emergency line is brought up to a percentage of its rated capacity such as percent. At this point is it desirable to switch the load from the utility line to the emergency line. If for any reason the emergency line fails, it may be desirable to switch back to the utility line and the sensor senses when the emergency line voltage diminishes beyond a certain percentage of normal capacity. After the cause of the utility line voltage drop has been remedied, the main line voltage rises; and when it reaches a pre-selected percentage of normal or rated value then it is desirable to discontinue the emergency supply and to transfer to the public utility line. Oscillation of the shaft 12 accomplishes the switching.

The outer end of shaft 12, which is preferably noncircular, is provided with an exposed lever 13 which may be manually used to move the shaft 12 through an approximately 60 travel as best shown in FIG. 3 where the solid line position of lever 13 indicates one position of the switch, and the dot-and-dash line position indicates the other position of the switch. Lever 13 is provided with a pin 14 which extends outwardly of the switch 11 and has a function hereinafter described. The electro-mechanical means for moving the lever 13 is contained in a housing 16 which is attached by bolts 17 to a flange 18 on the body of the switch 11. There is also provided an extension 19 outwardly of the housing 16 and detachably secured thereto which contains bearing 21 which supports the outer end of the shaft 12.

Mounted on opposite ends of the housing 16 are solenoids 23a, 23b. These solenoids have sufficient capacity to move the lever despite the mechanical holding the switch. Each solenoid has an armature 24 and the armatures are connected to each other by connecting bars 26 which are held in parallel positions on opposite sides of the armatures by transverse spacers 27 connected thereto by bolts 28. Also extending between the connecting bar 26 are rollers 29 and these rollers actually engage the lever 13 and by reason of the fact that they turn they overcome friction which might otherwise tend to prevent movement of the lever.

When either solenoid is energized, its armature 24 is retracted, pulling the bars 26 toward the solenoid and causing the opposite rollers 28 to pull the lever 13 to the full limit of its movement toward the energized solenoid. The lever 13 remains in such position because the switch 11 has a mechanical holding means internally thereof and hence it is unnecessary for the solenoid to continue to be energized.

To discontinue energization of solenoid 23a or 23b after it has moved lever 13 to the limit of its movement, cut-outs 31 are formed in the underside of the outer bar 26 so that the pin 14 may extend laterally into the extension 19 (see especially FIG. 1). Mounted on extension 19 are micro-switches 32a, 32!) each wired in series with solenoid 23a or 23b. Each switch 32 has a switch contactor 33 which opens the normally closed switch. Associated with each switch 32 is a spring 34 which is bent in a reverse bend 36 positioned so that when the pin 14 is moved to engage the bend 36 the spring 34 depresses the contactor 33 and opens the switch 32. The springs 34 and bends 36 cushion the contactors 33 against shock. Thus when the lever 13 has moved to the full limit of its travel, the switch 32 which is associated with the energized solenoid 23 is opened, de-energizing the solenoid and prolonging the life thereof.

The electro-mechanical means of the present invention may be used with a three-phase emergency line connected in the switch 11 by means of three pairs of contacts to the load lines. Also connected to the normal line is a sensing relay system which can sense when the voltage in any phase of the normal line falls below a certain percentage of normal capacity. A similar sensing relay is connected to the emergency lines which have leads also connected into the switch 11. When the shaft 12 is in normal position, the normal line contacts are in electrical contact with the load contacts. When the lever 13 is thrown through 60 of travel, then the emergency line contacts are connected to the load contact and the normal line contacts are disconnected from the load contacts. The sensing relays preferably through a control relay energize the lead wires to the switch 32a; and if the normally closed switch 32a is closed, then solenoid 23a is energized, causing the normal line contacts to be connected to the load in switch 11. Assuming this has taken place, then the pin 14 has caused the micro-switch 32a to open, de-energizing the solenoid 32a and it remains de-energized so long as the lever 13 is in the position shown.

If a sensor should sense any phase of the normal line voltage falling, then it causes the control relay, and, since the microswitch 32b is normally closed to energize, solenoid 23b, causing the lever 13 to be pulled to its opposite position, thereby opening the connection between the load contacts and the normal line contacts in switch 11 and closing the connection between the load contacts and the emergency line contacts. Usually the sensing relay also causes the emergency power line prime mover to be startedand there is a time delay which permits the emergency generator to come up to a percentage of its rated capacity before the sensing relay energizes the control relay.

When the normal line voltage has risen to say percent of its capacity, a sensing relay energizes the control relay to cause the switch 11 to switch to normal line position.

FIGS. 4 and 5 illustrate modification wherein an tric motor 46 is substituted for the solenoids 23a, b and is particularly useful where the size of the switching mechanism makes the movement thereof by solenoid control difficult. Many of the elements of the modification of FIGS. 4-5 are the same as in FIGS. 1-3; and, insofar as these elements are shown in FIGS. 4 and 5, the same reference numerals followed by subscript c are used to designate corresponding parts.

Motor 46 is reversible and is preferably considerably geared down. The shaft 47 of motor 46 is keyed to a circular cross-section brake disc 48. On opposite sides of disc 48 are plates 49 which are connected at one end by cross-member 51 formed at its end opposite motor 46 in clevis arms 52. Fitting between arms 52 is the radially extending lever 13c which is fixed to switch shaft 12c. Thus shaft 12c, lever 13c, and member 51 with its plates 49 oscillate together around the axis of shaft 120. Shaft 47 is concentric with shaft 12c and may extend into a hole in the end thereof as a bearing support one for the other. However, rotation of the two shafts is independent, except as explained below.

Engageable with the periphery of disc 48 is arcuate brake shoe 53 which is on the inner end of screw 54 threaded through member 51. By turning screw 54, shoe 53 may be brought into frictional contact with disk 48 and held in position by lock nut 56. When shoe 53 tightly engages disk 48, shafts 47 and 12c turn together. When there is an obstruction to movement of shaft (such as failure of micro-switches 32c, d to de-energize motor 46) then shoe 53 slips. When it is necessary to manually control switch 116 by lever 13c, screw 54 and nut 56 are loosened.

What is claimed is:

1. A control for a line transfer switch comprising a protruding oscillatory operating shaft and having switch means turned by said shaft, a lever extending perpendicular to said shaft, a housing fixed to said switch adjacent said lever, first and second solenoids carried by said housing on opposite sides of said lever and having first and second armatures, respectively, an open yoke fixed at opposite ends to said armatures on one side of said shaft, said lever extending up through said yoke to a position where it may be manually gripped for oscillating said shaft independent of said solenoids, said yoke having lever engaging means positioned so that when said first armature is fully extended from said first solenoid said lever is turned as far toward said second solenoid as said lever can move; and when said second armature is fully extended from said second solenoid, said lever is turned as far toward said first solenoid as said lever can move, a pin extending from said lever parallel to said shaft, a first and a second micro-switch on said housing each having an actuating arm engaged by said pin, said pin opening said first micro-switch when said lever is as far toward said first solenoid as said lever can move and said pin opening said second micro-switch when said lever is as far toward said second solenoid as said lever can move,

eleceach said micro-switch being wired in series with one side of said lever, said lever engaging means comprises of said solenoids. rollers rotatable between said bars on opposite ends of 2. A control according to claim 1 in which said yoke said bars relative to said lever.

comprises two spaced connecting bars, one on each 

1. A control for a line transfer switch comprising a protruding oscillatory operating shaft and having switch means turned by said shaft, a lever extending perpendicular to said shaft, a housing fixed to said switch adjacent said lever, first and second solenoids carried by said housing on opposite sides of said lever and having first and second armatures, respectively, an open yoke fixed at opposite ends to said armatures on one side of said shaft, said lever extending up through said yoke to a position where it may be manually gripped for oscillating said shaft independent of said solenoids, said yoke having lever engaging means positioned so that when said first armature is fully extended from said first solenoid said lever is turned as far toward said second solenoid as said lever can move; and when said second armature is fully extended from said second solenoid, said lever is turned as far toward said first solenoid as said lever can move, a pin extending from said lever parallel to said shaft, a first and a second micro-switch on said housing each having an actuating arm engaged by said pin, said pin opening said first micro-switch when said lever is as far toward said first solenoid as said lever can move and said pin opening said second micro-switch when said lever is as far toward said second solenoid as said lever can move, each said micro-switch being wired in series with one of said solenoids.
 2. A control according to claim 1 in which said yoke comprises two spaced connecting bars, one on each side of said lever, said lever engaging means comprises rollers rotatable between said bars on opposite ends of said bars relative to said lever. 